Fluid processing devices including microfluidic processing devices often require complicated control and valving arrangements to manipulate the flow of liquid samples through such devices. It would be desirable to provide a fluid processing device that would not require complicated valving or a separate system for effecting valving in the device. It would also be desirable to provide a device that enables the accurate and controlled manipulation of a liquid sample along a processing pathway that includes a plurality of different sample-containment regions.